I'm happy that I've raised six kids, and not one of them is a Ph.D.

The question that will decide our destiny is not whether we shall expand into space. It is: shall we be one species or a million? A million species will not exhaust the ecological niches that are awaiting the arrival of intelligence.

It is better to be wrong than to be vague.

We won't really understand the brain until we can make models of it which are analog rather than digital, which nobody seems to be trying very much.

Scientifically speaking, a butterfly is at least as mysterious as a superstring. When something ceases to be mysterious it ceases to be of absorbing interest to scientists. Almost all things scientists think and dream about are mysterious.

To me, mathematics is like playing the violin. Some people can do it - others can't. If you don't have it, then there's no point in pretending.

Computer models of the climate....[are] a very dubious business if you don't have good inputs.